MIAMI -- Catcher Jarrod Saltalamacchia will return from the 15-day disabled list on Thursday against the Mets to catch the Major League debut of Miami's top lefty prospect Andrew Heaney, at Marlins Park.

Saltalamacchia was put on the seven-day concussion list on June 1, and was transferred to the 15-day disabled list on Monday. Since Saltalamacchia had been on the disabled list for more than 15 days, he was eligible to be activated.

In two rehab games at Class A Jupiter -- one behind the plate and one as the designated hitter -- Saltalamacchia caught one full game and went 2-for-7 with a walk and a strikeout. Before the concussion, he was hitting .237 in 48 games for the Marlins this season.

After the 6-1 loss to the Cubs on Wednesday, the Marlins announced four roster moves that will become official on Thursday. They selected the contract of right-handed reliever Kevin Gregg from Triple-A New Orleans.

Gregg, who was signed to a Minor League contract on June 3, threw six innings in five appearances for the Zephyrs. He earned one win and recorded a 3.00 ERA.

Also on Wednesday, the team optioned lefty Dan Jennings to Triple-A New Orleans, and catcher J.T. Realmuto to Double-A Jacksonville.

The demotion of Jennings, who made 23 appearances and allowed five runs (two earned) on 24 hits, leaves just two left-handers in the Marlins bullpen.

Realmuto appeared in seven games in Saltalamacchia's absence and went 4-for-20.